java - 注入(inject)后的对象为空

Question

我正在尝试将单例对象注入(inject)到 2 个 Activity 中。
我的问题是，@Inject 之后的 Milk 和 Coffee 对象在 Activity 中为 null。在我看来，我错过了一些东西。
请帮助我并告诉我代码中缺少什么

应用程序组件:

@Singleton
@Component(modules = {CoffeeModule.class, MilkModule.class})
public interface AppComponent {

    @Component.Builder
    interface Builder {
        @BindsInstance
        Builder appModule(MyMvpApp myMvpApp);

        AppComponent build();

    }
    void inject(MyMvpApp app);
}

咖啡模块:

@Module
public class CoffeeModule {

    @Provides
    @Singleton
    Coffee getCoffee(){
        return new Coffee();
    }

}

牛奶模块:

@Module
public class MilkModule {

    @Provides
    @Singleton
    Milk getMilk(){
        return new Milk();
    }

}

我的类(class)应用程序:

public class MyMvpApp extends Application{

    @Override
    public void onCreate() {
        super.onCreate();
        initDagger();
    }

    private void initDagger() {
        AppComponent appComponent = DaggerAppComponent.builder()
                .appModule(this)
                .build();
        appComponent.inject(this);
    }

}

以及我的 Activity，这些对象为空:

public class LoginActivity extends AppCompatActivity {

    @Inject
    Milk milk;

    @Inject
    Coffee coffee;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        Log.i("tag", "" + milk + coffee);
    }
}

Answer 1

@Singleton
@Component(modules = {CoffeeModule.class, MilkModule.class})
public interface AppComponent {

  void inject(LoginActivity app);

  @Component.Builder
  interface Builder {
    @BindsInstance
    Builder appModule(MyMvpApp myMvpApp);

    AppComponent build();
  }
}



public class LoginActivity extends AppCompatActivity {
  @Inject
  Milk milk;

  @Inject
  Coffee coffee;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    DaggerAppComponent.builder().appModule((MyMvpApp) getApplicationContext()).build().inject(this);
    Log.i("tag", "" + milk + coffee);
  }
}


public class MyMvpApp extends Application {

  @Override
  public void onCreate() {
    super.onCreate();
    initDagger();
  }

  private void initDagger() {
    AppComponent appComponent = DaggerAppComponent.builder()
        .appModule(this)
        .build();
  }
}